First off: this book is beautiful. Hardcover, with a series of full-color plates 1/3rd and 2/3rds through. For only twice the price of a flimsy paperback, you're investing in five hundred solidly-constructed pages that will last.
And a good thing, because this book is destined to be a classic.
You don't need to have read Katz' other work, Wild Fermentation: The Flavor, Nutrition, and Craft of Live-Culture Foods, to understand, appreciate, and use this book - it stands alone. If you already own Wild Fermentation, don't be put off by the duplication of some recipes in the Table of Contents. Yes, sauerkraut, kimchi, and pickles are in here, but every section is greatly expanded with much more information and many more references. (Ever thought of using a layer of cooking oil as an airlock? Neither had I, but I'm going to try it!)
Speaking of references... the Resources, Glossary, and Works Cited chapters could keep you busy for a few years.
And yes: you will use this book. As Michael Pollan states in the well-written foreword, this is not one of those cookbooks you buy for the nice pictures and keep on your coffee table. This is a project manual. Fermentation is something you have to experience to understand, and Katz give you absolutely everything you need to get started. The first 67 pages are devoted entirely to the beginner, focusing not on specific recipes but on answering the inevitable questions: "WHY would I want to ferment food? is it safe? what equipment and general expertise do I need?"
Again from Pollan: "Katz writes about the transformative power of fermentation with such infectious enthusiasm that he makes you want to try things just to see what happens." This is so true. Even if you don't initially intend to, many of these 'recipes' are so simple and unintimidating (hard apple cider, mead, sauerkraut and its derivatives, sourdough) that it's hard to resist the urge to pick up a box of Mason jars and some fresh produce the next time you're at the grocery store. Many of us are experimenters at heart, and fermentation is the perfect mix of art and science to tap into this nature and inspire all kinds of crazy projects.
Already the neighborhood King of Kraut? I guarantee that this book will still have something for you. Chapter 12 - "Fermenting Meat, Fish, and Eggs" isn't enough? Turn to Chapter 13, for a short but serious discussion of what it takes to turn a fermentation hobby into a small business. Notes about scaleup, HACCP plans, and licensing are cool to read about, though I have no plans to open a tempeh factory anytime soon. Or how about Chapter 14 - "Non-Food Applications of Fermentation"? Again, I don't live on a farm, but it is neat to read about compost, silage, and bioremediation. (Surprise: Katz doesn't buy into corn ethanol biofuels)
While this is by no means a biology textbook, the scientific content is much improved over Wild Fermentation. Chapter 1 - "Fermentation as a Coevolutionary Force" is, in general, accurate and well-referenced. Katz is not a formally-trained scientist, but he does not shy away from technical details when they are helpful for understanding, and he shows respect for the scientific method and its results. See, for instance, his discussion of 'homofermentative' and 'heterofermentative' organisms in vegetable fermentation (pg 96), or of commercial starter cultures (pg 132).
If you subsist on white bread and margarine and bleach your cutting boards after every use, fermentation may not be the hobby for you. The first time I skimmed some strangely-textured yeast off of a crock of fermenting beets, I have to admit I was a little skeptical what those beets would look like when I pulled them out (they were absolutely delicious). While some of my more imaginative fermentation adventures have yielded delicious results, a few have been downright terrible (yep, ate them anyway!). If you don't see any issue with carving a bit of mold off some cheese or a piece of fruit instead of throwing it out, then you probably have what it takes.
Many (most?) of the poor reviews on Wild Fermentation are from people taking issue with Katz' lifestyle or philosophies. Many of his philosophical discussions in this book are backed up with hard science and references, so even those who found Wild Fermentation to be overbearing may find this new book to be more palatable. If you have some problem with the fact that Katz has HIV (he states this outright in the new book, and includes a sidebar about how fermented foods may be helpful but they are not a disease cure), do the rest of us a favor and keep it to yourself.
I've been experimenting with fermentation for about a year, relying mostly on Wild Fermentation and a substantial collection of online resources. I've only had this book for a week, and I've already had tons of fun and learned a lot. When I'm finished with my read-through, this book will definitely be making its rounds among my friends. A great reference and a worthwhile investment - highly recommended.